The present invention relates to a testing process for the quality control of electromagnetically actuated switching devices in which current contacts are made by actuating a magnetic armature. The testing includes a step of analyzing the vibrations or sound emissions from the switching devices occurring under operating conditions.
Carrying out functional testing and quality control of switching devices by means of an oscillation analysis during switching has already been proposed. The Japanese Patent Publication No. JP-A-01/80876 (hereinafter "the '876 publication") discusses a process for determining the contact force of a switching device. In the process of the '876 publication, vibration signals generated upon contact closure and armature closure are evaluated. Furthermore, a process of the type described at the beginning is discussed in the Russian Patent Publication No. SU-A-983 655 (hereinafter, "the '655 publication"). In the process of the '655 publication, the magnetic armature is operated with different currents in two different test cycles. The sound signals generated during this process are detected by means of an acoustic sensor and the quality of the switching device is derived therefrom. Finally, the Russian Patent Publication No. SU-A-1 272 374 (hereinafter, "the '374 publication") discusses an arrangement for the quality control of encapsulated reed contacts. In the process described in the '374 publication, the coil for the electromagnetically actuated contacts is excited and the oscillations generated by actuating the relay in the open and in the closed condition of the relay are detected and evaluated.
In addition, the Russian Patent Publication No. SU-A-907-623 (hereinafter "the '623 publication") discusses a process of the type mentioned above, in which oscillation and sound spectra are examined as a whole. Specific criteria for predicting future failure rates of a switching device are derived from the oscillations by means of statistical methods.
The object of the present invention is to improve the known testing processes by making the quality control objective. The process should be applicable to different electromagnetically actuated switching devices. Moreover, if any faults are present, the process should be able to classify them. Furthermore, the process should be able to evaluate noises in relays, in particular, motor vehicle flashing signal relays.